U.S. patent number 5,249,483 [Application Number 07/969,072] was granted by the patent office on 1993-10-05 for select shock reducing device of automotive automatic transmission.
This patent grant is currently assigned to JATCO Corporation. Invention is credited to Naonori IIzuka.
United States Patent |
5,249,483 |
IIzuka |
October 5, 1993 |
Select shock reducing device of automotive automatic
transmission
Abstract
In order to reduce a select shock of an automatic transmission,
a measure is employed, which comprises a first device for detecting
the selection of a drive range from a neutral range; a second
device for detecting the starting of engaging movement of a
hydraulically operated friction element for the drive range; a
third device for controlling a hydraulic pressure applied to the
friction element; a fourth device for causing the third device to
raise the hydraulic pressure to a higher level from the time when
the range selection is carried out to the time when the second
device detects the starting of engaging movement and lower the
hydraulic pressure to a lower level after the detection by the
second device; a fifth device for producing an instruction signal
when a predetermined time passes after the drive range detection by
the first device; and a sixth device for causing the third device
to lower the hydraulic pressure to the lower level upon issuance of
the instruction signal irrespective of any detection by the second
device.
Inventors: |
IIzuka; Naonori (Shizuoka,
JP) |
Assignee: |
JATCO Corporation (Fuji,
JP)
|
Family
ID: |
18066408 |
Appl.
No.: |
07/969,072 |
Filed: |
October 30, 1992 |
Foreign Application Priority Data
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Nov 1, 1991 [JP] |
|
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3-315526 |
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Current U.S.
Class: |
477/117 |
Current CPC
Class: |
F16H
61/061 (20130101); F16H 61/067 (20130101); F16H
61/08 (20130101); Y10T 477/6895 (20150115); F16H
2059/6807 (20130101); F16H 2061/0488 (20130101); F16H
2059/425 (20130101); F16H 2059/385 (20130101) |
Current International
Class: |
F16H
61/06 (20060101); F16H 59/68 (20060101); F16H
59/38 (20060101); F16H 61/04 (20060101); F16H
61/08 (20060101); F16H 061/06 () |
Field of
Search: |
;74/866 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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63-251652 |
|
Oct 1988 |
|
JP |
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01-105050 |
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Apr 1989 |
|
JP |
|
Primary Examiner: Wright; Dirk
Attorney, Agent or Firm: Foley & Lardner
Claims
What is claimed is:
1. A select shock reducing device of an automotive automatic
transmission comprising:
first means for detecting the selection of a drive range from a
neutral range;
second means for detecting the starting of engaging movement of a
hydraulically operated friction element for the drive range;
third means for controlling a hydraulic pressure applied to said
friction element;
fourth means for causing said third means to raise said hydraulic
pressure to a higher level from the time when said range selection
is carried out to the time when said second means detects said
starting of engaging movement and lower said hydraulic pressure to
a lower level after the detection by said second means; and
fifth means for producing an instruction signal when a
predetermined time passes after the drive range detection by said
first means; and
sixth means for causing said third means to lower said hydraulic
pressure to said lower level upon issuance of said instruction
signal irrespective of any detection by said second means.
2. A select shock reducing device as claimed in claim 1, in which
said predetermined time is varied in accordance with at least one
of the temperature of hydraulic fluid of the transmission, the
vehicle speed at the time when the range selection is carried out
and the engine load at the time when the range selection is carried
out.
3. A select shock reducing device as claimed in claim 1, in which
said first means is a select position switch which issues a signal
when a select lever is shifted from a neutral position to a forward
speed position.
4. A select shock reducing device as claimed in claim 1, in which
said second means uses an information signal produced by an input
shaft speed sensor by which the rotation speed of the turbine of an
associated torque converter is sensed.
5. A select shock reducing device as claimed in claim 4, in which
said second means detects the starting of engaging movement of the
friction element by sensing a speed down of said turbine.
6. A select shock reducing device as claimed in claim 1, in which
said third means is a line pressure control solenoid which controls
the line pressure of the transmission.
7. A select shock reducing device as claimed in claim 1, in which
said fifth means is a timer installed in a computer.
8. A select shock reducing device as claimed in claim 1, in which
said hydraulically operated friction element is a forward clutch.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates in general to automotive automatic
transmissions, and more particularly to a device for reducing a
select shock of the automatic transmissions.
2. Description of the Prior Art
In order to clarify the task of the present invention, one
conventional select shock reducing device for the automatic
transmission will be described, which is disclosed in Japanese
Patent First Provisional Publication 1-105050.
The select shock reducing device of this publication comprises
generally an accumulator which controls ON/OFF operation of
friction elements which are essential to all forward speeds and a
reverse, a sensor means which detects starting of engaging movement
of the friction elements, and a control means which raises the back
pressure of the accumulator for a period from the time when a new
range is selected by the transmission select lever to the time when
the sensor means detects the starting of engaging movement of the
friction elements. That is, when the transmission select lever is
moved from neutral to a range which will produce a forward speed,
the control means increases the back pressure of the accumulator to
raise hydraulic pressure applied to the friction elements. With
this, the starting of the engaging movement of the friction
elements is quickly carried out. When thereafter the sensor means
detects the starting of engaging movement of the friction elements,
the control means reduces the back pressure of the accumulator to a
normal level. With this, the accumulator can gently increase the
hydraulic pressure applied to the friction elements.
However, this conventional select shock reducing device has no
measure against a trouble of the sensor means. That is, when the
sensor means gets out of order, the starting of engaging movement
of the friction elements can not be detected, and thus, the
hydraulic pressure applied to the friction elements can not be
reduced to the normal level even when the engaging movement of the
friction elements starts. Thus, under such condition, the select
shock is deteriorated.
The sensor means employed in the select shock reducing device of
the publication is constructed to find the starting of the engaging
movement of the friction elements by detecting a reduction in
rotation speed of the turbine of the associated torque converter.
Thus, when the movement of the transmission select lever does not
induce a marked speed reduction of the turbine like in the
selection during cruising of the vehicle, it is impossible to sense
the starting of the engaging movement of the friction elements.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to provide a
select shock reducing device of automotive automatic transmission,
which is free of the above-mentioned drawbacks.
According to the present invention, there is provided a select
shock reducing device of an automotive automatic transmission,
which comprises first means for detecting the selection of a drive
range from a neutral range; second means for detecting the starting
of engaging movement of a hydraulically operated friction element
for the drive range; third means for controlling a hydraulic
pressure applied to the friction element; fourth means for causing
the third means to raise the hydraulic pressure to a higher level
from the time when the range selection is carried out to the time
when the second means detects the starting of engaging movement and
lower the hydraulic pressure to a lower level after the detection
by the second means; fifth means for producing an instruction
signal when a predetermined time passes after the drive range
detection by the first means; and sixth means for causing the third
means to lower the hydraulic pressure to the lower level upon
issuance of the instruction signal irrespective of any detection by
the second means.
BRIEF DESCRIPTION OF THE DRAWINGS
Other objects and advantages of the present invention will become
apparent from the following description when taken in conjunction
with the accompanying drawings, in which:
FIG. 1 is a schematic illustration of an automotive automatic
transmission to which the present invention is applied;
FIG. 2 is a TABLE showing ON/OFF conditions of various friction
elements of the automatic transmission with respect to speeds
selected by the transmission;
FIG. 3 is a hydraulic circuit of the automatic transmission;
FIG. 4 is a schematic view of a control unit for controlling the
transmission; and
FIG. 5 is a flowchart showing operation steps carried out in a
computer of the control unit.
DETAILED DESCRIPTION OF THE INVENTION
Referring to the drawings, there is shown an embodiment of the
present invention.
In FIG. 1, there is schematically shown an automotive automatic
transmission of a type having an overdrive, four forward speeds and
one reverse.
The transmission comprises an input shaft 13 to which a torque of
an engine output shaft 12 is transmitted through a torque converter
10. Designated by numeral 14 is an output shaft of the transmission
through which a driving force is fed to a final drive device (not
shown). Between the input and output shafts 13 and 14, there are
disposed, in the illustrated manner, a first planetary gear unit
15, a second planetary gear unit 16, a reverse clutch 18, a high
clutch 20, a forward clutch 22, an overrunning clutch 24, a
low-and-reverse brake 26, a band brake 28, a low-oneway clutch 29
and a forward-oneway clutch 30.
When the forward clutch 22 is engaged, the transmission is ready
for effecting a forward speed, and when the reverse clutch 18 and
the low-and-reverse brake 26 are engaged, the transmission is ready
for effecting a reverse. The forward clutch 22, the reverse clutch
18 and the low-and-reverse brake 26 constitute so-called "friction
elements" which are essential to all forward speeds and a
reverse.
The torque converter 10 has a lock-up clutch 11 installed
therein.
The first planetary gear unit 15 comprises a sun gear S1, an
internal gear R1, pinion gears P1 each meshing with both the sun
gear S1 and the internal gear R1, and a pinion gear carrier PC1
carrying the pinion gears P1.
The pinion gear carrier PC1 is connectable to the input shaft 13
through the high clutch 20, and the sun gear S1 is connectable to
the input shaft 13 through the reverse clutch 18.
The second planetary gear unit 16 comprises a sun gear S2, an
internal gear R2, pinion gears P2 each meshing with both the sun
gear S2 and the internal gear R2, and a pinion gear carrier PC2
carrying the pinion gears P2.
The pinion gear carrier PC1 of the first planetary gear unit 15 is
connectable to the internal gear R2 of the second planetary gear
unit 16 through the forward clutch 22 and the forward-oneway clutch
30 which are connected in tandem or through the overrunning clutch
24 which is arranged in parallel with the tandem connected clutches
22 and 30.
The sun gear R2 of the second planetary gear unit 16 is constantly
connected with the input shaft 13, and the internal gear R1 of the
first planetary gear unit 15 and the pinion gear carrier PC2 of the
second planetary gear unit 16 are constantly connected with the
output shaft 14.
The low-and-reverse brake 26 can fix the pinion gear carrier PC1 of
the first planetary gear unit 15 and the band brake 28 can fix the
sun gear S1 of the first planetary gear unit 15.
The low-oneway clutch 29 is so arranged as to permit only a normal
rotation (viz., the rotation in the same direction as the engine
output shaft 12) of the pinion gear carrier PC1 of the first
planetary gear unit 15. That is, a reversed rotation of the pinion
gear carrier PC1 is suppressed by the clutch 29.
By selectively engaging and disengaging the clutches 18, 20, 22,
24, 29 and 30 and the brakes 26 and 28 in various combinations, the
elements (viz., S1, S2, R1, R2, PC1 and PC2) of the first and
second planetary gear units 15 and 16 are forced to change their
operating conditions. With this changing, the ratio of rotation
speed of the output shaft 14 relative to that of the input shaft 13
can be variously changed.
FIG. 2 is a table showing the various gear speeds (viz., first,
second, third and fourth forward speeds and a reverse) which are
given by the ON/OFF conditions of the clutches 18, 20, 22, 24, 29
and 30 and the brakes 26 and 28.
In the table, the mark "O" means "ON" or engaged condition of the
associated clutch or brake and "blank" means "OFF" or disengaged
condition of the same. The mark "(O)" means engaged condition of an
associated clutch or brake. However, this engaged condition does
not participate in power transmission in the established gear
speed. It is to be noted "a1" or "a2" is a ratio of the number of
teeth of the sun gear S1 or S2 relative to that of the internal
gear R1 or R2, and the "GEAR RATIO" is the ratio of the rotation
speed of the input shaft 13 relative to that of the output shaft
14.
FIG. 3 shows a hydraulic control circuit for controlling operation
of the above-mentioned automatic transmission. The control circuit
comprises a line pressure control valve 40, a pressure modifier
valve 42, a line pressure control solenoid 44 (viz., control means
for controlling hydraulic pressure applied to the "friction
elements"), a modified pressure accumulator 46, a pilot valve 48, a
torque converter relief valve 50, a lock-up control valve 52, a
first shuttle valve 54, a lock-up control solenoid 56, a manual
valve 58, a first shift valve 60, a second shift valve 62, a first
shift solenoid 64, a second shift solenoid 66, a servo-charger
valve 68, a 3-2 timing valve 70, a 4-2 relay valve 72, a 4-2
sequence valve 74, a first reducing valve 76, a second shuttle
valve 78, an overrunning clutch control valve 80, an overrunning
clutch solenoid (viz., engine brake controlling solenoid) 82, an
overrunning clutch reducing valve 84, a 1-2 accumulator 86, a 2-3
accumulator 88, a 3-4 accumulator 90, a N-D accumulator 92, an
accumulator control valve 94 and a filter 96. These elements are
connected in such a manner as is shown in the drawing.
The torque converter 10 has therein pressure apply and release
chambers 11a and 11b for the lock-up clutch 11. This torque
converter 10, the forward clutch 22, the high clutch 20, the band
brake 28, the reverse clutch 18, the low-and-reverse brake 26 and
the overrunning clutch 24 are connected to the hydraulic control
circuit in the illustrated manner. The band brake 28 has a pressure
apply chamber 28a for the second speed, a pressure release chamber
28b for the third speed and a pressure apply chamber 28c for the
fourth speed incorporated therewith.
An oil pump 34 of capacity variable vane type, an oil cooler 36, a
front lubrication circuit 37 and a rear lubrication circuit 38 are
connected in the illustrated manner. The oil pump 34 is equipped
with a feedback accumulator 32.
The hydraulic control circuit of this type is described in detail
in Japanese Patent First Provisional Publication No. 63-251652.
FIG. 4 shows schematically a control unit 300 which controls the
operation of the solenoids 44, 56, 64, 66 and 82. As shown, the
control unit 300 comprises an input interface 311, a reference
pulse generator 312, a central processing unit (CPU) 313, a read
only memory (ROM) 314, a random access memory (RAM) 315 and an
output interface 316, an address bus 319 and a data bus 320.
Information signals from an engine speed sensor 301, a vehicle
speed sensor 302, a throttle valve opening degree sensor 303, a
select position switch 304 (viz., select range detecting means), a
kick down switch 305, an idle switch 306, a full throttle switch
307, an oil temperature switch 308, an input shaft speed sensor 309
for detecting the rotation speed of the turbine of the torque
converter and an over-drive switch 310 are fed to the input
interface 311 of the control unit 300.
The controlled operation of the select shock reducing device of the
present invention is carried out in such a manner as is depicted in
the flowchart of FIG. 5.
That is, at step 152, the rotation speed "Nt" of the turbine of the
torque converter 10, which is sensed by the input shaft speed
sensor 309, is read. Then, at step 154, a judgement is carried out
as to whether or not the transmission select lever has been moved
from neutral (viz., "Neutral" position or "Parking" position) to a
range for producing a forward speed. If "No", that is, when the
select lever has not been moved to such range, the routine flows to
step 166 wherein the drive duty ratio "D" of the line pressure
control solenoid 44 is set to a predetermined value "D1" and then
the routine flows to step 170 to finish the control. While, if
"Yes" at step 154, that is, if the select lever has been moved to
such range, the routine flows to step 156 wherein the change rate
".DELTA.Nt" of the rotation speed "Nt" is calculated. Then, the
routine flows to step 158 wherein a judgement is carried out
whether or not the change rate ".DELTA.Nt" is equal to or greater
than a predetermined value "A". If "Yes", the routine flows to the
above-mentioned step 166. While, if "No", that is, if the change
rate ".DELTA.Nt" is smaller than the predetermined value "A", the
routine flows to step 160 wherein the time "T" taken from the time
when the select lever has come to the new range is read. The
routine then flows to step 162 wherein a judgement is carried out
as to whether or not the elapsed time "T" is equal to or greater
than a predetermined value "Ta". If "Yes", the routine flows to the
step 166. While, if "No", that is, if the elapsed time "T" is
smaller than the predetermined value "Ta", the routine flows to
step 164 wherein the drive duty ratio "D" is set to another
predetermined value "D2", and the control is finished at step
170.
It is to be noted that when the drive duty ratio "D" is "D1", the
line pressure, that is, hydraulic pressure applied to the forward
clutch 22 exhibits a lower level, while, when the drive duty ratio
"D" is "D2", the hydraulic pressure exhibits a higher level. That
is, the accumulator control valve 94 is controlled by the line
pressure which is adjusted by the line pressure control solenoid
44, and the hydraulic pressure obtained by this control is applied
to the N-D accumulator 92 as a back pressure. In accordance with
this back pressure, the degree of the hydraulic pressure applied to
the forward clutch 22 is determined.
In the transmission, the following operation is practically carried
out in accordance with the above-mentioned control flow.
When the transmission select lever is moved from a neutral range
(for example, "N" range) to a forward speed range (for example, "D"
range), this movement is sensed by the select position switch 304
and a timer is set running. At the same time, the control unit 300
issues an instruction signal to the line pressure control solenoid
44 for raising the hydraulic pressure, which is applied to the
forward clutch 22, to the predetermined higher level. When the time
predetermined by the timer elapses, or when the rotation speed of
the torque converter turbine is lower than a predetermined value,
the control unit 300 issues an instruction signal to the solenoid
44 to lower the hydraulic pressure of the forward clutch 22 to the
predetermined lower level. That is, upon issuance of either a
signal representing expiration of the time predetermined by the
timer or another signal representing reduction in rotation speed of
the torque converter turbine, the hydraulic pressure applied to the
forward clutch 22 is controlled from the higher level to the lower
or normal level. Accordingly, even when the speed sensor 309 can
not detect the speed reduction of the torque converter turbine due
to its failure or the like, the needed reduction in hydraulic
pressure applied to the forward clutch 22 is assuredly carried out
by the timer. Thus, the undesirable select shock is assuredly
eliminated or at least minimized.
Since the temperature of the hydraulic oil, the vehicle speed, and
the engine load tend to affect the engaging timing of the forward
clutch 22, the predetermined time set by the timer may be changed
in accordance with at least of them.
* * * * *